Aluminum-based alloy composition and method of making extruded components from aluminum-based alloy compositions

ABSTRACT

The present invention involves an aluminum-based alloy composition for vehicle components. The composition consists essentially of between about 0.15 to 0.6% weight silicon to provide recrystallization, between about 0.2 to 0.7% weight iron, between about 0.4 to 0.6% weight copper, between about 1.1 to 1.4% weight manganese, between about 0.15 to 0.3% weight magnesium, between about 0.15 to 0.4% weight zinc, between about 0.1 to 0.15% weight zirconium, and the balance aluminum.

BACKGROUND OF THE INVENTION

The present invention relates to aluminum alloy compositions and methods of making extruded components from aluminum alloy compositions using conform extrusion.

Extrusion processes have been common practice for several years in various industries for hot forming of aluminum alloys. The extrusion of aluminum has been termed one of the most versatile processes known. Its many applications in everyday use prove the versatility of both the process and the metal.

Conventional extrusion involves casting the material in long logs, and removed from the cast and cut into billet lengths of between about 24 to 36 inches each. The billets are then placed in a heating process typically called homogenizing. During the homogenizing process, the non-aluminum elements of the billets are dissolved and brought to desirable discrete bodies with the aluminum. To produce an aluminum extrusion, a cylindrical ingot is preheated to a temperature of around 450° Celsius and is forced at a high pressure of up to 830 MPa through a shaped orifice in a hardened steel die.

The resulting shapes and lengths of aluminum alloy of constant cross-section may be solid or hollow (enclosing voids), simple or exceedingly complex. Furthermore, these shapes have all the desirable characteristics looked in for wrought products including an adequate metallurgical structure which can be bent, formed, forged, machined, or welded. The conventional extrusion process can achieve production of highly intricate shapes, production of accurate shapes, provision of hinge features for moving assemblies, provisions of shapes that assemble with minimum fixing, production of a single shape to replace several parts, and provision of local strength and stiffening.

Although current conventional extrusion processes are adequate, improvements may be made. For example, a typical extrusion apparatus/machine may occupy a substantial area of about 6 feet by 30 feet. Moreover, a conventional extrusion process requires cutting of each billet length to between about 24 to 36 inches, and preheating the billets to about 400° C., thereby resulting in a relatively timely consuming and substantial source of power. Furthermore, for each billet loaded in the extrusion operation, the system requires stoppage.

BRIEF SUMMARY OF THE INVENTION

The present invention generally provides an alloy composition resulting in improved corrosion resistance and reduced die wear during die usage. This result is accomplished by adding predetermined levels of copper to the alloy to improve the corrosion resistance, zirconium to improve grain size after a brazing operation, manganese to improve strength and reduce grain growth. Moreover, an addition of a predetermined balanced proportion of zinc, magnesium and silicon to the alloy results in creating a relatively large number of small grain size after the brazing operation.

The present invention involves an aluminum-based alloy composition for vehicle components such as vehicle heat exchanger tubes. The composition consists essentially of between about 0.15 to 0.6% by weight silicon to provide recrystallization, between about 0.2 to 0.7% by weight iron, between about 0.4 to 0.6% by weight copper, between about 1.1 to 1.4% by weight manganese, between about 0.15 to 0.3% by weight magnesium, between about 0.15 to 0.4% by weight zinc, between about 0.1 to 0.15% by weight zirconium, and the balance is aluminum.

In another embodiment, the present invention includes a method of conform extruding an aluminum-based heat exchanger tube. The method comprises pressing the aluminum-based alloy composition and forming a formable alloy composition to a predetermined configuration of the aluminum-based heat exchanger tube.

In yet another embodiment of the present invention, the method includes coining the aluminum-based alloy composition to shear the alloy composition, and shearing the composition to preheat the aluminum-based alloy composition, defining the formable alloy for providing formability of the alloy composition. The method further includes propelling the formable alloy composition, and forcing the formable alloy composition through a die to a predetermined configuration of the aluminum-based heat exchanger tube.

Further objects, features, and advantages of the present invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a table depicting an aluminum-based alloy composition for vehicle components in accordance with one embodiment of the present invention;

FIG. 2 is a systems diagram of a conform extrusion process for extruding the aluminum-based alloy composition in accordance with one example of the present invention;

FIG. 3 a is a schematic diagram of a conform extrusion process for extruding the aluminum-based alloy composition to form an aluminum-based heat exchanger tube;

FIG. 3 b is an enlarged view of circle 3 b in FIG. 3 a of the conform extrusion process; and

FIG. 4 is a flow chart depicting one method of conform extruding an aluminum-based heat exchanger tube in accordance with one example of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention provide an aluminum-based alloy composition and methods of making components, e.g., vehicle heat exchanger tubes, from the aluminum-based alloy composition. The present invention provides a solution to concerns of apparatus size, efficiency, while maximizing in recrystallization and minimizing grain growth of the composition.

Generally, the composition includes added silicon for a reduced die wear, for enhanced die life, and for minimal grain growth. Recrystallization of the composition is further maximized with the use of copper, magnesium, and zinc. Grain growth of the composition is minimized by the use of zirconium, chromium, and manganese. Moreover, it is preferred that the silicon percent weight is relatively low, between about 0.15 and 0.30 to promote recrystallization. Additionally, it is to be understood that the composition is absent any titanium or chromium to minimize die wear.

FIG. 1 is a table 10 illustrating the elements comprising the aluminum-based alloy composition in accordance with one embodiment of the present invention. As shown, the aluminum-based alloy composition includes silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), zinc (Zn), and zirconium (Zr). Preferably, the alloy composition consists essentially of 0.15 to 0.60 Si weight (wt.) percent (%), 0.2 to 0.7 Fe wt %, 0.4 to 0.6 Cu wt %, 1.1 to 1.4 Mn wt %, 0.15 to 0.30 Mg wt. %, 0.15 to 0.40 Zn wt %, and 0.10 to 0.15 Zr wt %.

Although, not wanting to be limited by theory, it is believed that copper, magnesium, zinc, and silicon promote recrystallization of the alloy composition, and zirconium, chromium, and manganese minimize grain growth of the alloy composition.

In this embodiment, the alloy composition may be extruded to form vehicle components suitable for manufacturing air conditioning products, e.g., heat exchanger tubes. It has been found that, when extruded via a conform extrusion process, the alloy composition has the ability to restrict the grain size for suitable application. It has also been found that the composition has the ability to enhance corrosion resistance of a finished product, thereby extending the life of the product.

FIG. 2 illustrates a systems diagram 110 depicting a typical conform extrusion process line for the production of aluminum-based heat exchanger tubes from the aluminum-based alloy composition provided in the table of FIG. 1. In accordance with one embodiment of the present invention, the system comprises a feedstock pay-off unit 112. The feedstock pay-off unit 112 receives feedstock alloy composition to be casted therein into 9.5 to 12 millimeter feedstock rods. The feedstock rods are then pulled into a feedstock straightener unit 114. In this embodiment, both the feedstock pay-off unit 112 and the feedstock straightener 114 are non-powered units, since a conform machine (mentioned below) downstream has sufficient power to pull the feedstock rod through the feedstock units.

To free the feedstock rods from oxide, oil, grease, and any other contaminants, the rods are fed through a feedstock cleaning system 116. This system may be any suitable system such as an ultrasonic system or a parorbital system. As known in the art, the principle of the parorbital system is a combined mechanical and chemical cleaning action.

For example, the parorbital system may include a plurality of cleaning heads, wherein each cleaning head comprises entry and exit air knives to prevent the escape of cleaning fluid, and a plurality of hydro-converters which perform the cleaning. In this example, each hydro-converter may contain two tungsten carbide dies of slightly larger diameter than the feedstock rod. A high velocity jet of cleaning fluid may then be injected into the hydro-converter in such a way to create a vortex around the feedstock rod. The vortex of fluid causes the feedstock rod to orbit at high speeds, and scrubs the surface of the rod against the tungsten carbide dies.

The alloy composition material is then coined to fit into the conform extruder. As shown in FIG. 2, the system 110 further includes a conform process system 118. As described in greater detail below, the conform process includes a conform machine comprising a grooved wheel and shaft assembly. In the conform extruder, the composition is pressed through a die apparatus and is formed into a finished shape of a tube exiting the conform machine.

The conform line may be controlled by a computer system having software configured to provide desired features (listed below). For example, the features may be as follows: measurement and recording of operating parameters such as temperatures, speeds, and machine loads; tabular display of primary, secondary, and control parameters; graphic display on one second time base of any four primary parameters over the last 24 hours; graphic display on 1/10 second time base of any four control parameters; file recording of primary, secondary, and control parameters; review of recorded files; control of dynamic systems such as heaters and alarms; calibration of system inputs and outputs; and setup and calibration of control loops. Other features may be included without falling beyond the scope or spirit of the present invention.

As further shown in FIG. 2, a cooling system 120 cools the tube which are then coiled. The tube is then cut to a predetermined length. No heat treatment is necessary. For example, the cooling system 120 for the extrusion wheel and tooling may comprise of a storage tank with a product cooling trough mounted on top. The rear of the tank may be a pumping station containing a pump and a heat exchanger for each cooling circuit. A high volume pump can maintain the required level and flow velocity of the product cooling circuit. The low volume circuits may supply cooling to the extrusion wheel and tooling. Flow control valves for each of the cooling circuits may be mounted on the front of the tank and a closed system may be used to enable the water contacting the product and tooling circuits to be softened.

Special features of the cooling system may be developed to control the cooling rate of the product upon leaving the extrusion die. A rapid quench or a more gradual cooling rate is possible. This in turn, assists in regulating the grain structure and hence properties of the extruded component.

FIG. 3 a illustrates a schematic view of a conform extrusion machine 210 for extruding an aluminum-based vehicle component, e.g., a heat exchanger tube, from an aluminum-based alloy composition. In accordance with one embodiment of the present invention, the conform extrusion machine 210 includes a rotary wheel 212 that rotates to carry feedstock material through the machine 210. The rotary wheel 212 comprises a groove 214 radially formed thereon in which the feedstock material is fed. The conform machine 210 further includes a pivot or shearing shoe 216 to which the rotary wheel 212 is adjacently disposed. As shown, the shoe 216 cooperates with the rotary wheel 212 to form a lid on the groove 214 as the feedstock material is carried through the groove 214, coining the feedstock material. Extrusion pressure is generated as the shoe 216 covers the groove 214.

The machine 210 further includes an abutment 220 integrally connect to the shoe 216 and configured to cooperate with the rotary wheel 212. The abutment 220 dams the material to be extruded. As the feedstock material is carried in the groove 214, the abutment 220 causes the material to be sheared against the shoe 216, resulting in superheating of the material and defining a formable alloy. The material generates frictional heat and modification heat, i.e., temperatures of up to 500 degrees or more can be reached without using a heater. As the feedstock material is carried in the groove 214, the material is maintained in a high plastic flow state due to the modification to the shear direction at the abutment 220 and the high temperature.

Additionally, during the process, the extruded material is recrystallized, and is in a “tempered” state. Moreover, since the form of feedstock material is a wire rod, in this embodiment, it is possible to extrude continuously without having to stop the machine in order to join pieces of material together.

The machine 210 further comprises an extrusion chamber 222 having an extrusion die 224 through which the material is extruded after passing the abutment 220. The abutment 220 is formed to cooperate with the rotary wheel 212 and to provide a dam of the material to be extruded, thereby forcing the material through the extrusion chamber 222. In use, the abutment 220 forces the material to be propelled to the extrusion chamber 222. The material is forced through the die 224 to be formed into a predetermined configuration of the aluminum-based heat exchanger tube. Since the metallic wire is manufactured by continuous cast and rolling, it is relatively inexpensive and straightforward to make a relatively large coil of two tons or more. Furthermore, as shown, for machine is configured to allow a limited amount of scrap to flow away from the abutment.

It is to be understood that any suitable apparatus may be used to make the conform extrusion machine operable in accordance with the present invention. For example, the conform machine may be mounted in rollerbearings that incorporate multiple seals to retain oil and prevent ingress of foreign material. A separate pressurized, filtered and cooled lubrication system insures that the bearings may be adequately lubricated and correct operating temperatures are maintained. The bearings may be held in a rugged steel frame that is extended to carry the pivot shoe and a hydraulic shoe retaining system. The relative deflections of the wheel and tooling may be kept to a minimum, enabling adequate product tolerances to be maintained, despite the relatively high operating forces involved. The main shaft may be driven by an infinitely variable, controlled DC electric motor, via a gear box. The power output envelope of the drive may be matched to the production rates specified or desired.

Additionally, the pivot shoe that carries the tooling may be inserted and retracted by hydraulic cylinders operated from the pendant control panel on the machine. When closed, the shoe may be clamped in place by hydraulic cylinders. The system gives easy start up conditions and minimizes the risk of damage from overload when operating an unfamiliar product, since the clamp pressure can be released, allowing the shoe to back off.

FIG. 4 illustrates a flow chart of one method 310 of conform extruding an aluminum-based heat exchanger tube in accordance with one example of the present invention. As shown, the method 310 comprises pressing an aluminum-based alloy composition consisting essentially of the following elements:

between about 0.15 to 0.6% by weight of silicon to reduce die wear of the conform extruder; between about 0.2 to 0.7% by weight of iron; between about 0.4 to 0.6% by weight of copper; between about 1.1 to 1.4% by weight of manganese; between about 0.15 to 0.3% by weight of magnesium; between about 0.15 to 0.4% by weight of zinc; between about 0.1 to 0.15% by weight of zirconium to reduce grain growth, and the balance being aluminum to define a formable alloy for providing formability of the alloy.

Preferably, the temperature of the composition during the step of pressing ranges between about 4000 Celsius (C) and 500° C. More preferably, the temperature is at about 480° C. In this embodiment, the step of pressing includes coining the aluminum-based alloy composition to shear the alloy composition and shearing the composition to superheat the aluminum-based composition to define the formable alloy for providing formability of the alloy.

The method 310 further includes forming the formable alloy to a predetermined configuration of the aluminum-based heat exchanger tube. In this embodiment, the step of forming includes propelling the formable alloy to the extrusion chamber of the conform extrusion machine and forcing the formable alloy through the extrusion die to the predetermined configuration of the aluminum-based heat exchanger tube.

Preferably, as mentioned, the extrusion die is held in a pivoting shoe in the die chamber. The die chamber holds the abutment(s) that fit into the wheel groove(s) and divert the flow of the alloy into the die chamber. The die chamber insures accurate alignment the tooling and allows tooling to be pre-assembled for rapid changes. In this embodiment, the die chamber accommodates a wide range of product dies.

While the present invention has been described in terms of preferred embodiments, it will be understood, of course, that the invention is not limited thereto since modifications may be made to those skilled in the art, particularly in light of the foregoing teachings. 

1. An aluminum-based alloy composition for vehicle components, consisting essentially of: between about 0.15 to 0.6% by weight of silicon to provide recrystallization; between about 0.2 to 0.7% by weight iron; between about 0.4 to 0.6% by weight copper; between about 1.1 to 1.4% by weight manganese; between about 0.15 to 0.3% by weight magnesium; between about 0.15 to 0.4% by weight zinc for reducing grain growth; between about 0.1 to 0.15% of weight zirconium, and the balance aluminum.
 2. The composition of claim 1 wherein the balance aluminum includes a ratio of manganese to iron of between about 1 and 3 for high corrosion resistance and formability.
 3. The composition of claim 1 wherein the zinc is between about 0.25 and 0.4% by weight.
 4. The composition of claim 1 wherein the silicon is of the form of dymagnesium silicide.
 5. The composition of claim 1 wherein the Vickers hardness of the intermetallic phases is between about 5,000 and 10,000.
 6. The composition of claim 1 wherein the grain size of the composition is less than about 60 μm.
 7. An aluminum-based alloy composition for vehicle heat exchanger tubes, consisting essentially of: between about 0.15 to 0.6% weight silicon; between about 0.2 to 0.7% weight iron; between about 0.4 to 0.6% weight copper; between about 1.1 to 1.4% weight manganese; between about 0.15 to 0.3% weight magnesium; between about 0.15 to 0.4% weight zinc; between about 0.1 to 0.15% weight zirconium, and the balance aluminum, the ratio of manganese to iron is between about 1 and 3, for high corrosion resistance and formability.
 8. The composition of claim 7 wherein the zinc is between about 0.25 and 0.4% weight.
 9. The composition of claim 7 wherein the zinc content is about 0.25% weight.
 10. The composition of claim 7 wherein the silicon is of the form of dimagnesium silicide.
 11. The composition of claim 7 wherein the Vickers hardness number is between about 5,000 and 10,000.
 12. The composition of claim 7 wherein the grain size of the alloy is less than about 60 μm.
 13. A method of conform extruding an aluminum-based vehicle component, the method comprising: pressing an aluminum-based alloy composition consisting essentially of: between about 0.15 to 0.6% by weight silicon to reduce die wear of the conform extruder; between about 0.2 to 0.7% by weight iron; between about 0.4 to 0.6% by weight copper; between about 1.1 to 1.4% by weight manganese; between about 0.15 to 0.3% by weight magnesium; between about 0.15 to 0.4% by weight zinc; between about 0.1 to 0.15% by weight zirconium to reduce grain growth, and the balance aluminum; to define a formable alloy for providing formability of the alloy; and forming the formable alloy to a predetermined configuration of the aluminum-based vehicle component.
 14. The method of claim 13 further comprising: providing a conform extrusion machine for extruding the aluminum-based vehicle component; and introducing feedstock of the aluminum-based alloy to the conform extrusion machine.
 15. The method of claim 14 wherein the feedstock is a feed rod of between about 9 and 12 mm diameter.
 16. The method of claim 13 wherein pressing includes: coining the aluminum-based alloy composition to shear the alloy composition; and shearing the composition to superheat the aluminum-based composition to define the formable alloy for providing formability of the alloy.
 17. The method of claim 13 wherein the temperature is between about 400° C. and 500° C.
 18. The method of claim 13 wherein the temperature is about 480° C.
 19. The method of claim 13 further comprising: providing a conform extrusion machine having an extrusion die through which the formation alloy is pressed.
 20. The method of claim 13 wherein forming includes: propelling the formable alloy; and forcing the formable alloy through a die to the predetermined configuration of the aluminum-based vehicle component. 